The German Offenlegungsschrift 102 00 230 A1 discloses a stirrer driving mechanism for upright and horizontal reactors. It is in the form of a hydraulic motor, which is disposed directly in the reactor, the product, used in the reactor, being used as hydraulic medium for driving purposes. The hydraulic medium is supplied over a pipeline to the driving mechanism and the driving energy is generated by an external pump station. After the transfer of the driving power for the stirrer, this product is introduced as reactant into the reactor and caused to react further here.
If there is a malfunction or breakdown in the case of this solution, the driving mechanism for the reaction process, which is disposed in the reactor, must be shut down and the repair made by opening the reactor to the atmosphere. Moreover, controlling the process by using a signal of a measured parameter of the driving system is not employed here. The use of the product as a hydraulic medium would also have the disadvantage here that the product, as a result of the process-related temporal changes in its consistency, would not have a constant basis for producing independent signals for process control.
The patent DE 40 13 912 C2 introduces a horizontally aligned reactor, which is equipped with an externally acting and an internally acting rotor, the rotors rotating within one another and scraping the product from their wetted surfaces for efficient mixing and distribution of the product for producing a large surface area and a therewith associated high degree of degassing. The use of the two driving mechanisms, required for this purpose, and the resulting distance of the centers of gravity of the driving system from the reactor wall are disadvantages of this device. Moreover, the arrangement of the scraper rotor in the cage-like rotor, which makes the equipment expensive, may be a possible cause of malfunctioning with regard to maintaining the clearances between the scraper elements and the washers of the squirrel cage rotor and with regard to the long rotor length and the possible transverse deflection of the rotors.
The DE 44 47 422 C2 publication discloses a reactor device, which is provided with a rotor with lattice-like excavations in the hollow body and with mounted perforated disks and spoke wheels. In the interstices of the perforated disks and the spoke wheels, weir arrangements and scraping rods are installed in the region of the polymer bottom at the reactor wall. The reactor is divided over its length into zones by decreasing the intervals and varying the angle of incidence of the perforated disks and the spoke wheels on the hollow body or changed geometrically in accordance with the consistency of the product. With this solution, the objective is pursued of achieving, with a simple construction, an improved stability against twisting and deflection, as well as good mixing and uniformity of the residence time of the product and, with that, a high product quality. In this solution also, the arrangement of the weirs and the scraping rods between the perforated disks and spoke wheels is a disadvantage with respect to possible warping and with that, contacts by forces from the product during rotor movement.
The German Offenlegungsschrift 100 01 477 A 1 discloses a discontinuous polycondensation method with a stirring disk reactor. This reactor is designed for discontinuous operation, in which the moment adjusts as a function of the viscosity, which increases with the time during which the vacuum is applied. There is no control, such as is required in a continuous process. The geometry of the stirring disk reactor is also clearly designed for a discontinuous operation.
The AS 1745541 discloses a polycondensation method and a device, in which an annular disk reactor is described. This annular disk reactor consists of several zones, which, however, are constructed strictly as annular disks. There is no description of reaction material being taken up actively on the annular disks. Moreover, the annular disks produce high friction, which become noticeable negatively in the form of temperature increases and must be corrected. The use of variable-speed drives is expensive and the process data cannot be used in this configuration as an active component of the control of the process.
AS 1495665 introduces a method and a device for the continuous throughput of melts for the production of polycondensation products. This construction is distinguished essentially by annular backing-up elements. In addition, there are spreading and distributing devices. The backing-up elements, described in this construction, are disadvantageous from a chemical engineering point of view, since reaction material can build up on these back-up elements, be decomposed thermally over time and affect product quality. In this device also, comparatively little reactive surface area is produced. This would necessarily drive up the dimensions in the case of high throughputs.
AS 1645630 discloses a devices, honeycombed by partitions, for the polycondensation of liquid pre-condensates. The stirring elements are helical. This supports the transport of the reaction material in the direction of the product exit. An expensive construction of chamber walls is required for this device. It is difficult to achieve a homogeneous mixing of the product due to the chambers. Furthermore, the residence time, produced by the chambers, counteracts the positive transport of the reaction product in the direction of the product discharge.
The Offenlegungsschrift 1570939 introduces polymerization equipment, in which the reaction material is transported through the equipment by means of cage-like screw segments or courses without a shaft. Due to the srew-like nature of the construction, the reaction material is transported in a clearly accelerated fashion, so that the residence time is reduced and consequently, for larger throughputs, the dimensions of the equipment must be increased. The control of the parameters of the reaction material, which is now required in up-to-date equipment, is not dealt with at all.
The Offenlegungsschrift 1925093 discloses a device for completing the condensation of polycondensation products. With the device here, an attempt is made over a plurality of different built-in components, some of which are very complicated, and different disks and scraper components to produce a reactive surface. The built-in components introduced tend to become contaminated and to cause thermal decomposition of adhering material. Built-in components must therefore be realized as simply as possible.
In none of the publications searched was a measure found for using process parameters from the operation of the rotor and their effect for controlling the process. Furthermore, the use of heavy driving mechanisms with a relatively large distance between the center of gravity and the front side of the reactor is not satisfactory or the configuration of the rotors frequently is expensive. The large weight of the driving aggregates with relatively long lever arms are responsible for the exertion of large bending forces on the rotors, the rotor shafts, the front sides of the reactors and the sealing system for the vacuum existing in the reactor. During the operation of the reactor, these large bending forces have a negative effect on the reactor as a whole and on the gaps between the reactor elements and the built-in components, especially if sliding surfaces are used with a minimum clearance between rotor elements and associated housing elements or internally running rotors.
It is an object of the invention to provide a device for the treatment of flowable, highly viscous or pasty media under a vacuum, such as polyesters or other polymers, which uses measured parameters from the operation for the selective, sensitive control of the process with the objective of producing very high quality values for the product up to an intrinsic viscosity of 0.9 dl/g and, furthermore, by using suitable driving mechanisms, achieves minimization of the static and dynamic forces acting on the reactor and, by advantageous design of the reactor and the rotors, improves the method and the operation.